7.6.1.2. Routers in case of packet forwarding

Older Linux kernel (at least <= 2.4.17) don't support default routes. You can set them up, but the route lookup fails when a packet should be forwarded (normal intention of a router). If you're still using such older kernel, “default routing” can be setup using the currently used global address prefix “2000::/3”.

Note: take care about default routing without address filtering on edge routers. Otherwise unwanted multicast or site-local traffic can leave the edge.